The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. Teletype Corporation's Model 33 terminal, introduced in 1963, was one of the most popular terminals in the data communications industry until the late 1970s. Over a half-million 33s were made by 1975, and the 500,000th was plated with gold and placed on special exhibit. Another 100,000 were made in the next 18 months, and serial number 600,000, manufactured in the United States Bicentennial, was painted red, white and blue, and shown around the country. The Model 33 was one of the first products to employ the newly standardized ASCII character encoding method, which was first published in 1963. A companion Teletype Model 32 used the older, established five-bit Baudot code. Because of its low price and ASCII compatibility, the Model 33 was widely used, and the large quantity of teleprinters sold strongly influenced several de facto standards that developed during the 1960s. The Model 33 originally cost about $1000 (equivalent to $11,000 today), much less than other teleprinters and computer terminals in the mid-1960s, such as the Friden Flexowriter and the IBM 1050. In 1976, a new Model 33 RO printer cost about $600 (equivalent to $3,000 today). As Teletype Corporation realized the growing popularity of the Model 33, it began improving its most failure-prone components, gradually upgrading the original design from "light duty" to "standard duty", as promoted in its later advertising (see advertisement). The machines had good durability and faced little competition in their price class, until the appearance of Digital Equipment Corporation's DECwriter series of teleprinters.
It is less rugged and cost less than earlier Teletype models. The Teletype Corporation introduced the Model 33 as a commercial product in 1963, after it had originally been designed for the United States Navy. The Model 33 was produced in three versions:
Model 33 ASR (Automatic Send and Receive), which has a built-in eight-hole punched tape reader and tape punch; Model 33 KSR (Keyboard Send and Receive), which lacks the paper tape reader and punch; Model 33 RO (Receive Only) which has neither a keyboard nor a reader/punch.
Naming conventions While the manufacturer called the Model 33 teleprinter with a tape punch and tape reader a "Model 33 ASR", many computer users used the shorter term "ASR-33". The earliest known source for this equipment naming discrepancy comes from Digital Equipment Corporation (DEC) documentation, where the September 1963 PDP-4 brochure calls the Teletype Model 28 KSR a "KSR-28" in the paragraph titled "Printer-Keyboard and Control Type 65". This naming convention was extended from the Teletype Model 28 to other Teletype equipment in later DEC documentation, consistent with DEC's practice of designating equipment using letters followed by numerals. For example, the DEC PDP-15 price list from April 1970 lists a number of Teletype Corporation teleprinters using this alternative naming convention. This practice was widely adopted as other computer manufacturers published their documentation. For example, Micro Instrumentation and Telemetry Systems marketed the Teletype Model 33 ASR as "Teletype ASR-33". The trigram "tty" became widely used as an informal abbreviation for "Teletype", often used to designate the main text input and output device on many early computer systems. The abbreviation remains in use by radio amateurs ("ham radio") and in the hearing-impaired community, to refer to text input and output assistive devices.
Obsolescence Early video terminals, such as the Tektronix 4010, did not become available until 1970, and initially cost around $10,000 (equivalent to $105,000 today). However, the introduction of integrated circuits and semiconductor memory later that decade allowed the price of cathode-ray tube-based terminals to rapidly fall below the price of a Teletype teleprinter. "Dumb terminals", such as the low-cost ADM-3 (1975) began to undercut the market for Teletype terminals. Such basic video terminals, which could only sequentially display lines of text and scroll them, were often called glass Teletypes ("glass TTYs") analogous to the Teletype printers. More-advanced video terminals, such as the Digital Equipment Corporation VT52 (1975), the ADM-3A (1976), and the VT100 (1978), could communicate much faster than electromechanical printers, and could support use of a full-screen text editor program without generating large amounts of paper printouts. Teletype machines were gradually replaced in new installations by much faster dot-matrix printers and video terminals in the middle-to-late 1970s. (A malfunctioning Teletype served as a plot point in the 1971 science fiction film The Andromeda Strain). Because of falling sales, Teletype Corporation shut down Model 33 production in 1981. Some remained in working use, as with a scientific project in Australia, in which one was connected to a phase ionosonde (to investigate the ionosphere) until 1984.
Technical information
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